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Optimizations and applications in large-scale scenes of Monte Carlo geometry conversion code CMGC

Nuclear Science and Techniques 2025年第4期36卷 220-232页

作者： Xin Wang Ling-Yu Zhang Xue-Ming Shi Zhen Wu Jun-Li Li Gui-Ming Qin Yuan-Guang Fu CAEP Software Center for High Performance Numerical Simulation Beijing 100088China Institute of Applied Physics and Computational Mathematics Beijing 100088China Department of Engineering Physics Tsinghua UniversityBeijing 100084China

In response to the demand for rapid geometric modeling in Monte Carlo radiation transportation calculations for large-scale and complex geometric scenes,functional improvements,and algorithm optimizations were performed using CAD-to-Monte Carlo geometry conversion(CMGC)*** representation(BRep)to constructive solid geometry(CSG)conversion and visual CSG modeling were combined to address the problem of non-convertible geometries such as spline *** splitting surface assessment method in BRep-to-CSG conversion was optimized to reduce the number of Boolean operations using an Open ***,in turn,reduced the probability of CMGC conversion *** auxiliary surface generation algorithm was optimized to prevent the generation of redundant auxiliary surfaces that cause an excessive decomposition of CAD geometry *** optimizations enhanced the usability and stability of the CMGC model *** was applied successfully to the JMCT transportation calculations for the conceptual designs of five China Fusion Engineering Test Reactor(CFETR)*** rapid replacement of different blanket schemes was achieved based on the baseline CFETR *** geometric solid number of blankets ranged from hundreds to tens of *** correctness of the converted CFETR models using CMGC was verified through comparisons with the MCNP calculation *** CMGC supported radiation field evaluations for a large urban scene and detailed ship *** enabled the rapid conversion of CAD models with thousands of geometric solids into Monte Carlo CSG *** analysis of the JMCT transportation simulation results further demonstrated the accuracy and effectiveness of the CMGC.

关键词： Monte Carlo CAD BRep to CSG CMGC

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Self-consistent pressure-dependent on-site Coulomb correction for zero-temperature equations of state of f-electron metals

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Physical Review B 2025年第11期111卷 115139-115139页

作者： Bei-Lei Liu Yue-Chao Wang Xingyu Gao Hai-Feng Liu National Key Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing 100094 China

The f-electron materials display many anomalous properties under pressure, making them of great interest in high-pressure physics and related industrial fields. However, the f-electrons pose a substantial challenge to simulations since the electron correlation effects. In this work, we present a first-principles calculation scheme for the equations of state (EoS) of f-electron materials. The self-consistent pressure-dependent on-site Coulomb correction is performed based on our recently developed doubly screened Coulomb correction approach. We investigated pressure dependence of the on-site Coulomb interaction, zero-temperature EoS over a wide range of pressures and the phase stabilities of four prototypical lanthanide and actinide metals, Pr, Eu, Th, and U. The simulated compressive properties agree better with the experimental data than those obtained by conventional density functional theory (DFT) and fixed-parameter DFT+U approaches. The pressure-induced phase transitions can also be well described.

关键词： Coulomb interactions

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Kinetics of Rayleigh-Taylor instability in van der Waals fluid:the influence of compressibility

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Frontiers of physics 2025年第1期20卷 269-297页

作者： Jie Chen Aiguo Xu Yudong Zhang Dawei Chen Zhihua Chen National Key Laboratory of Transient Physics Nanjing University of Science and TechnologyNanjing 210094China National Key Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsP.O.Box 8009-26Beijing 100088China State Key Laboratory of Explosion Science and Safety Protection Beijing Institute of TechnologyBeijing 100081China HEDPS Center for Applied Physics and Technologyand College of EngineeringPeking UniversityBeijing 100871China National Key Laboratory of Shock Wave and Detonation Physics Mianyang 621999China School of Mechanics and Safety Engineering Zhengzhou UniversityZhengzhou 450001China

Early studies on Rayleigh−Taylor instability(RTI)primarily relied on the Navier−Stokes(NS)*** research progresses,it becomes increasingly evident that the kinetic information that the NS model failed to capture is of great value for identifying and even controlling the RTI process;simultaneously,the lack of analysis techniques for complex physical fields results in a significant waste of data *** addition,early RTI studies mainly focused on the incompressible case and the weakly compressible *** the case of strong compressibility,the density of the fluid from the upper layer(originally heavy fluid)may become smaller than that of the surrounding(originally light)fluid,thus invalidating the early method of distinguishing light and heavy fluids based on *** this paper,tracer particles are incorporated into a single-fluid discrete Boltzmann method(DBM)model that considers the van der Waals *** using tracer particles to label the matter-particle sources,a careful study of the matter-mixing and energy-mixing processes of the RTI evolution is realized in the single-fluid *** effects of compressibility on the evolution of RTI are examined mainly through the analysis of bubble and spike velocities,the ratio of area occupied by heavy fluid,and various entropy generation rates of the *** is demonstrated that:(i)compressibility has a suppressive effect on the spike velocity,and this suppressive impact diminishes as the Atwood number(At)*** influence of compressibility on bubble velocity shows a staged behavior with increasing.(ii)The impact of compressibility on the entropy production rate associated with the heat flow(S_(NOEF))is related to the stages of RTI ***,this staged impact of compressibility on S_(NOEF)varies with *** exhibits an inhibitory effect on the entropy production rate associated with viscous stresses(S_(NOEF)).(iii)By incorporating the morphological parameter of the pr

关键词： discrete Boltzmann method Rayleigh-Taylor instability compressibility effect tracer particles

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Soliton resolution for the energy-critical wave equation with an inverse-square potential in the radial case

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Science China mathematics 2025年

作者： Xuanying Li Changxing Miao Lifeng Zhao School of Mathematical Sciences University of Science and Technology of China Institute of Applied Physics and Computational Mathematics

In this paper, we present the soliton resolution for the energy-critical wave equation with an inverse square potential in the radial case and all dimensions N≥3. A crucial ingredient of our analysis involves the energy channel for the linearized wave equation with inverse square potentials, which incorporates the distorted Hankel transform.

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Theoretical investigation of the laser-induced three-dimensional vibration excitation of neutral N2Ar

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Physical Review A 2025年第4期111卷 042822-042822页

作者： Ting Xu YinSong Tang Xiaoqing Hu JinPeng Ma SiQi Pei CongCong Jia Yong Wu JianGuo Wang National Key Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing 100088 China

In this paper, the laser-driven three-dimensional vibration excitation dynamics of N2Ar dimer are simulated using the full time-dependent wave-packet simulation method. The three-dimensional vibrational wave functions are obtained first by solving the Schrödinger equation involving the rotation of N2, vibration of N2-Ar, and intermolecular interaction. The solved vibration wave functions have both the angular quantum number m and the symmetric or antisymmetric properties with respect to the N2-Ar axis. The theoretical calculation shows that laser-induced molecular vibrational excitation needs to satisfy the selection rules of nonresonant Raman processes. Two modes of excitation are further distinguished as follows: (1) Δm=±2 and the symmetry does not change; here, the van der Waals bond will be strengthened. (2) Δm=±1 and the symmetry is reversed; here, the dimer will be partially excited into a linear structure. Our results point out that the N2Ar initially located in the ground vibrational state mainly prefers the excitation of mode (1), but the one located in the first excited state will undergo two modes of excitation simultaneously.

关键词： Van der Waals forces

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Adaptive Uncertainty Quantification for Stochastic Hyperbolic Conservation Laws

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SIAM-ASA Journal on Uncertainty Quantification 2025年第2期13卷 339-374页

作者： Harmon, Jake J. Tokareva, Svetlana Zlotnik, Anatoly Swart, Pieter J. Eulerian Codes Group X Computational Physics Division Los Alamos National Laboratory Los AlamosNM87545 United States Applied Mathematics and Plasma Physics Group Theoretical Division Los Alamos National Laboratory Los AlamosNM87545 United States

We propose a predictor-corrector adaptive method for the study of hyperbolic partial differential equations (PDEs) under uncertainty. Constructed around the framework of stochastic finite volume (SFV) methods, our approach circumvents sampling schemes or simulation ensembles while also preserving fundamental properties, in particular hyperbolicity of the resulting systems and conservation of the discrete solutions. Furthermore, we augment the existing SFV theory with a priori convergence results for statistical quantities, in particular push-forward densities, which we demonstrate through numerical experiments. By linking refinement indicators to regions of the physical and stochastic spaces, we drive anisotropic refinements of the discretizations, introducing new degrees of freedom where deemed profitable. To illustrate our proposed method, we consider a series of numerical examples for nonlinear hyperbolic PDEs based on Burgers' and Euler's equations. © 2025 Society for Industrial and applied mathematics and American Statistical Association.

关键词： Stochastic systems

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Formation mechanism of multiple spallation and its penetration induced by shear localization in NiTi alloy under implosion loading

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Matter and Radiation at Extremes 2025年第1期10卷 81-97页

作者： Xianye Wu Xiaoyang Pei Xiang Chen Hao Zhang Jin Wang Xin Yang Meizhen Xiang Shang Gao Fang Wang School of Materials and Energy Southwest UniversityChongqing 400715China Institute of Fluid Physics China Academy of Engineering PhysicsMianyang 621999China State Key Laboratory of Nuclear Physics and Technology Center for Applied Physics and TechnologyPeking UniversityBeijing 100871China School of Environment and Resource Southwest University of Science and TechnologyMianyang 621010China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China

This study uses nonequilibrium molecular dynamics simulations to explore the dynamic failures and deformation mechanisms of a cylindrical shell composed of nanocrystalline nickel-titanium alloy under implosion *** discover that some individual spall planes are sequentially generated in the material along the propagation of a radial stress wave,indicative of the formation of multiple *** larger grain sizes,void nucleation at the first spallation occurs in a coexisting intergranular/transgranular manner,whereas with decreasing grain size,voids tend to nucleate along the grain ***,the spall strength exhibits a transition from an inverse Hall-Petch to a Hall-Petch *** larger grain sizes,at the secondary spallation,localized shearing zones and grain boundaries provide potential void-nucleated ***,the formation of shear deformation bands promotes grain refinement,contributing to a reduction in the dislocation-induced strengthening ***,a lower spall strength is produced,in contrast to the first *** the grain size becomes smaller,voids nucleate mostly along grain boundaries,and plastic deformation is dominated by dense grain ***,the high temperature caused by shear localization leads to material weakening,and in turn there is a significant decrease in the spall strength for the secondary spallation,compared with the ***,significant penetration between two spall planes is observed for large grain size,which can be attributed to the nucleation of voids on linking grain boundaries,with temperatures exceeding the melting point of the material.

关键词： grain alloy deformation

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High order direct discontinuous Galerkin method for elliptic interface problem on arbitrary polygon fitted meshes

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Computers and mathematics with Applications 2025年 191卷 144-166页

作者： Guo, Hanlin Yin, Li Cui, Xia of China Academy of Engineering Physics Beijing100088 China Institute of Applied Physics and Computational Mathematics Beijing100088 China National Key Laboratory of Computational Physics Beijing100088 China

In this article, we aim to develop a high order direct discontinuous Galerkin (DDG) method solving elliptic interface problem on arbitrary polygon fitted meshes. Elliptic interface problem with the homogeneous or non-homogeneous interface conditions can be solved in the uniform discrete DDG formulation. Numerical analysis results show that high order DDG method for polygonal elliptic interface problem on arbitrary polygon fitted meshes can reach the optimal kth order convergence in H1 norm and the optimal (k+1)th order convergence in L2 norm. By refining meshes nearby the curved interface, errors coming from polygonal approximating interface can be reduced. A sequence of numerical experiments are carried out to verify the optimal convergence of DDG method with high order P2, P3 and P4 approximations to deal with several different interface situations. It means that DDG method is capable of handing interface problems with complicated geometries meshes and interface situations. © 2025

关键词： Convergence of numerical methods

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The chemisorption thermodynamics of O2 and H2O on AFM UO2 surfaces unraveled by DFT+U-D3 study

arXiv

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arXiv 2025年

作者： Huang, Yang Zhang, Le Ji, Hefei Zhang, Zhipeng Zhang, Qili Sun, Bo Liu, Haifeng Song, Haifeng Institute of Applied Physics and Computational Mathematics Beijing100094 China Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing100088 China Institute of Materials China Academy of Engineering Physics Jiangyou621907 China

Unraveling the adsorption mechanism and thermodynamics of O2 and H2O on uranium dioxide surfaces is critical for the nuclear fuel storage and uranium corrosion. Based on the first-principles DFT+U-D3 calculations, we carefully test the effect of antiferromagnetic order arrangements on the thermodynamic stability of UO2 surfaces and propose the 1k AFM surface computational model. The chemisorption states of O2 and H2O on UO2 (111) surface, suggested by previous experiments, are accurately calculated for the first time. The adsorption properties of O2 and H2O on UO2(111) and (110) surfaces are discussed in detail to reveal the different interaction mechanisms. Combined with ab initio atomistic thermodynamics method, we systematically calculate the chemisorption phase diagram and isotherm of O2 and H2O on UO2 surfaces. Due to the different intermolecular interactions, the monolayer and multilayer adsorption models are identified for O2 and H2O, respectively. This study has comprehensively revealed the different adsorption mechanisms of O2 and H2O on UO2 surfaces, bridging the electronic structure calculations to the interpretation of experimental results and providing a solid foundation for future theoretical studies of uranium corrosion mechanism in humid air. Copyright © 2025, The Authors. All rights reserved.

关键词： Uranium dioxide

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Chemical reaction mechanisms and models of energetic materials: A perspective

Energetic Materials Frontiers

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Energetic Materials Frontiers 2025年第1期6卷 129-144页

作者： Meng, Li Song, Qing-guan Yao, Chuang Zhang, Lei Pang, Si-ping School of Materials Science & Engineering Beijing Institute of Technology Beijing100081 China Institute of Applied Physics and Computational Mathematics Beijing100088 China Institute of Chemical Materials China Academy of Engineering Physics Mianyang621999 China of Chongqing School of Materials Science and Engineering Yangtze Normal University Chongqing408100 China

Energetic materials (EMs) are a kind of metastable functional materials with certain potential barriers, overcoming which can quickly release the energy stored in EMs. A thorough understanding of reaction mechanisms and accurate quantification of reaction rates are fundamental issues for optimizing energy output, ensuring hazard mitigation, and assessing the safety levels of EMs. This perspective provides an overview of research progress in chemical reaction mechanisms and models, with a particular emphasis on organic EMs and reactive metals. Organic EMs are mainly composed of carbon, hydrogen, nitrogen, and oxygen elements, enabling supersonic and self-sustaining detonation reactions capable of significant energy output. The incorporation of reactive metals like aluminum, magnesium, and boron has been recently found to augment the combustion heat and explosion temperature of EM formulations, sparking heightened research interest. This perspective first presents both EMs’ reaction mechanisms revealed via multiscale simulations and experimental methods, including thermal decomposition, shock initiation, and post combustion. Then, quantitatively characterized expressions of the physical models derived from the revealed mechanisms, including mathematical expressions like elementary and phenomenological reaction kinetic models, and emerging data-driven machine learning models, are reviewed. Finally, the view of the application, existing problems, and further development directions are outlined. © 2024 The Authors

关键词： Reaction rates

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